The present invention relates to a swash-plate type compressor for use in air conditioners for vehicles or the like, and more particularly to lubrication of the bearing portions supporting the drive shaft as well as the sliding portions between the swash plate and the pistons.
As known, e.g., from U.S. Pat. No. 3,801,227, a conventional compressor of this kind is typically constructed such that a pair of cylinder blocks are combined together in axial alignment and horizontally disposed. The cylinder blocks each include an axial through bore extending along the axis thereof, through which bore a drive shaft extends. A swash plate is secured on the drive shaft. Each one pair of valve plates and cylinder heads are mounted on the outer ends of the combined cylinder blocks. The cylinder blocks further include a plurality of cylinder bores axially extending therethrough, in each of which a piston is slidably received. The cylinder bore, the piston and the valve plate deline in cooperation a pumping chamber therebetween. The swash plate has its outer fringe disposed in engagement with the pistons in such a manner that rotation of the drive shaft causes the pistons to make reciprocating motions within the cylinder bores by means of the swash plate, for pumping action. The drive shaft is supported in the radial directions by radial bearings mounted within the through bores and in the axial directions by thrust bearings arranged at opposite sides of the swash plate.
With this arrangement, lubrication of the radial bearings, the thrust bearings and the sliding portions between the swash plate and the pistons is carried out due to a pressure differential produced in the compressor. More specifically, an oil reservoir is provided beneath the swash plate chamber between the cylinder blocks. Lubricating oil stored in the oil reservoir is splashed into a mist by the swash plate being rotated in unison with rotation of the drive shaft, and the misty oil is supplied to the thrust bearings arranged at the opposite sides of the swash plate and the sliding portions between the swash plate and the pistons. Simultaneously, due to a pressure differential between the swash plate chamber and the radial bearing sections which is caused by the reciprocating motions of the pistons within the cylinder bore which are in communication with the swash plate chamber, part of the misty oil fed to the thrust bearings is delivered to the radial bearings through gaps between the drive shaft and the axial through bores.
However, according to the above-mentioned pressure differential lubrication, due to the supply of lubricating oil in the form of a mist to various sliding portions in the compressor an inadequate amount of lubricating oil is supplied to these portions, causing insufficient lubrication of same. Further, the supply of lubricating oil to the sliding portions depends upon the concentration of the lubricating oil used, so that stable lubrication may not be obtained.